1. Field of the Invention
The invention relates to a locking device, in particular, in a motor vehicle, with a key-activated cylinder core which performs locking functions upon rotation. For a rotational support of the cylinder core a cylinder guide is provided having stopping points for tumblers positioned within the cylinder core. In order to make the locking device theft-proof, an overload protection device is provided which is comprised of, on the one hand, an axially fixed profiled control element and a profiled counter control element that is axially movable and spring-loaded against the profiled control element. An overload situation occurs when, without key, a forced rotation is exerted on the cylinder core. In this case, the profiled counter control element is axially lifted off the profiled control element and decouples a turning member relative to the cylinder core, and the cylinder guide is freely rotatable relative to the cylinder core because the cylinder core is fixedly connected thereto by the tumblers. The turning member is now inactive, while normally, upon actuation by the key, it performs the desired locking function, for example, in a lock.
2. Description of the Related Art
In a known locking device of this kind (DE 41 22 414 C1) the profiled control element and the profiled counter control element of the overload securing device are arranged between the housing and the overload protection device while the coupling is realized between the turning member and the cylinder core. The cylinder guide is axially spring-loaded relative to the housing. Between the housing and the cylinder guide a large annular space for a coil spring which surrounds a portion of the cylinder guide must be arranged. Mounting of these components is cumbersome and time-consuming. The transition of the normal situation into the overload situation results in an axial movement of the cylinder guide together with the cylinder core supported therein because the profiled control element of the overload protection device is lifted off the profiled counter control element. This is disruptive. This disruptive axial movement from the normal situation into the overload situation can be oriented axially outwardly (compare FIGS. 1 through 9) or axially inwardly (compare FIG. 10).
There are also locking devices of the aforementioned kind (DE 44 10 783 C1) in which the cylinder guide is not spring-loaded and, together with the cylinder core supported therein, always has an axially fixed position within the housing. In the transition between the key-activated normal situation into the overload situation resulting from the use of a burglary tool, the cylinder core therefore does not perform a disruptive axial movement. Moreover, radial space is also saved in this context because there is no pressure spring acting on the cylinder guide.
The disadvantage of this device is however the large axial construction length. The profiled control element and the profiled counter control element of the overload protection device are arranged between the inner end face of the cylinder guide and a pressure ring which is longitudinally slidable but rotationally fixedly connected to the turning member performing the locking function.
The invention has the object to develop a locking device of the aforementioned kind in which the cylinder guide and the cylinder core are axially fixedly received in the housing and freely rotatable in the overload situation, but characterized by a minimal axial construction length.
In accordance with the present invention, this object is solved in that:
for rotationally supporting the cylinder core a cylinder guide is provided which has stopping points for tumblers located in the cylinder core;
the cylinder guide is received axially fixed but rotatably in a housing that supports the cylinder guide in the area facing the
key, while the other area of the cylinder guide is surrounded by a sliding member fixed against rotation relative to the cylinder guide but axially slidably supported thereon, wherein the sliding member is surrounded by a turning member that is rotatable relative to the sliding member and synchronously axially movable with it;
a spring supported on the housing acts axially on the turning member and thus onto the sliding member synchronously movable with the turning member;
an overload protection device has a profiled control element arranged on the housing and a profiled counter control element, arranged on the sliding member and spring-loaded against the profiled control element, for axially moving the sliding member and the turning member synchronously movable therewith in the overload situation in order to release an axial coupling whose one coupling member is non-rotatingly fixedly connected to the cylinder core and whose other coupling member is arranged on the turning member.
The housing supports only an area of the cylinder guide facing the key while the other area of the cylinder guide is surrounded by a sliding member which is secured against rotation relative to the cylinder guide but is axially slidable thereon. The sliding member is surrounded by the turning member that transmits the locking functions and is rotatable relative to the sliding member and axially synchronously movable with it. The spring serving as overload protection acts axially onto the turning member and thus onto the sliding member which is movable synchronously with the turning member. The profiled elements of the overload protection device are arranged between the sliding member, on the one hand, and the housing provided for supporting the cylinder guide, on the other hand. According to the invention, the profiled elements of the overload protection device can be arranged easily in that axial portion of the cylinder core where the cylinder core has the tumblers and the cylinder guide the stopping points for the tumblers. This results in a reduction of the axial construction length relative to the latter prior art.